The World Health Organization defines anemia in adults and children older than 15 years as a hemoglobin concentration (Hb) <13.0 g/dL in male individuals and <12.0 g/dL in female individuals. In children aged 1.5 to 5 years anemia is defined as Hb <11 g/dL, in those 5 to 12 years as <11.5 g/dL, and in those 12 to 15 years as <12 g/dL (1).
The Hb falls as GFR falls, but the relationship is nonlinear. In hemodialysis patients, Hb often falls below 8 g/dL if anemia is untreated, whereas in nondialysis patients with chronic kidney disease (CKD) patients, higher Hb levels are usual unless the patients are close to initiating dialysis or have another contributing cause.
The initial investigation of anemia should include a complete blood count, absolute reticulocyte count, serum ferritin and transferrin saturation to diagnose iron deficiency, and serum B12 and folate levels to diagnose rare but treatable vitamin deficiencies. A high index of suspicion for gastrointestinal blood loss in the presence of iron deficiency is advisable.
The three major interventions to treat anemia in patients with CKD include iron, erythropoiesis-stimulating agents (ESAs), and blood transfusions. An individualized approach to anemia therapy was stressed by the KDIGO Work Group, in which the potential benefits of the therapy (avoidance of blood transfusions and improvement of anemia-related symptoms) were balanced against the risk of harm caused by the intervention, rather than a group approach targeting particular ranges of Hb.
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